In testing another change in the caching code, I switched this from TRUE to FALSE.

When it was TRUE, the inbox was not setting messages as being read.

When I turned off caching, it started working normally.

Question about this though: it says when TRUE, cache messages & mailbox data in local database.
When this is FALSE, does this make it cache to the TEMP directory, or instead it just stops caching at all?

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// enable caching of messages and mailbox data in the local database.
// this is recommended if the IMAP server does not run on the same machine
$rcmail_config['enable_caching'] = FALSE;
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